It is known that a magnetic field of a magneto-inductive flow measuring device is produced by a clocked direct current of alternating polarity. This assures a stable zero-point and makes the measuring insensitive to influences of multiphase materials, in homogeneities in the liquid or low conductivity. In such case, methods are known, with which the coil arrangement can be operated. These methods have already led to improvement for time efficient operation of the coil arrangement.
In known methods, for example in European patent, EP 1 460 394 A2, the supply voltage is controlled by direct reversing of an applied overvoltage down to a holding voltage. This direct reversing has, however, the result that eddy-currents are induced, which oppose a fast reverse poling of the magnetic field.